Manufacture of iron shot



March 7, 1961 L. P. wlLsoN ErAL 2,974,031

MANUFACTURE OF IRON SHOT Original Filed April 20, 1953 2 Sheets-Sheet 1 Q00 QG00O00\0O0%69060 eoeooooooooooocaxvooo 4 March 7,1961 1 RWILSON nu 2,974,031

MANUFACTURE OF IRON SHOT Original Filed April 20. 1953 2 Sheets-Sheet 2 INVENTORS.

LEWIS P. WILSON and ROBERT LJURNER, oEcD.

United States Patent MANUFACTURE OF IRON SHOT Lewis 1.. wilson, Edwardsville Township, Madison County, lll., and Robert L. Turner, deceased, late of Alton, lll., by Dorothy H. Turner, executrix, New

Haven. County, Coun., assiguers to, Olin Mathieson Cllenlicalv Corporation, a; corporation, 0i Virginia This invention relates tothe/:treatment otironshicti particularly to, a, process. of manufacturing ,the same with properties Such, that 'alterare adapted, for :use tas A.the projectile' Charge in Shot. gun ammunition Thslanpli- @fion is@ division 0f pending; application, Serial No, 349,612, led April 20, 1953, now Patent No. 2,867,554, which is a continuation in part of abandoned application, Serial No, 130,122, tiled November 30, 1949.

5027113121136 Yeats, the bulls Vof projectiles,madefbyx the: Sn 11s ammuuitiouindustw hasi consistedo leadierits, alloys in. spite of known. disadrantages and: undesirable. features, of the use of themetal lead..V One disadvantage is theVV tendency Qt' a. leadprojectile, when. subjected: tov the heat and driving force of the burning powder, to

, foul or lead the barrel, and is due to the exceptional softness ofthe metal' and its low;melting-point.v Another disadvantage off the use4 of' an. exceedingly soft'ymetal',V such as lead shot, is that the impact of initially'rspheri# cal pellets of lead. with each' otherandfth'einter-ior of'a gunv barrel causes; deformation of; the shot, which their pass through the air toward:- thetarget with. unequal` velocities in, a. lengthening shot string,` which isl notasI effective on a swiftly moving target as ashorts-shot string; Still another disadvantage ofthe use of lead' isl its, great` density, whichA makeslead-z unsuitable for usetashay high velocity projectile designed primarily'for exceptional eff fectiveness at short ranges. the fuse` ofilead, panticularly asshotg is thepoisonous*ua-V turesof themetal, which not'only:causes-contamination of game in which such` shotu haslodged; butf also will cause the deathe of wild fowl inhabiting-feeding; grounds on-which shot has accumulated over afpe'ric'ndl of manyv years. Furthermore, the high-cost` of lead; asv compared".

tothe cost of other commo metals and-materials-,lis` a' serious economic disadvantage, d

Attempts to 'overcome the disadv'ant-ages' of" lead'A shot` have been-made.v For example, soft 'leadshot have been' plated with various.` metals, such? 'asA tin, zinc; andcopp'er; to preventv shot deformationaand-,banrel leadingg ln other instances, hard lead alloys,- or=` leadf alloys 4arndlenaljle to hardening, have been used? to produce chilledmi lead shot. The above-notedand;similarftreatments Ahayehot'A avoided the use of leadand inmany `instances ,arejatf- 60 Although iron shot wassuggestedas a'projectile as tended by the -cost of additional stepsf"andiequipmentgj early as the beginning ofthe fteenth century, 'andal-f though, as early as theiyear'lSSO; the'NWinthferliches-Q1- aware of the economic-'advantage offusingmfor sporting ammunition a dropped shot of viron insteadoflead,v obtained two United 'Statespatents,jnamelyNo. 224,5 858 `and No, 236,134, in' which disclosure is Qmade offa method of manufacture and-the'advantages ofiiron.

2,974,031 Patented Mar. 7,

Ice

soh'ard as to damagethe gun barrels. Even 'the/hard-l ened gun barrels of the present dayaerode seriously when used with iron shot oflthe character heretofore sug"- gested. The damage is accentuated since the introduc-A tion vof the use ofsmokeless powder and high velocity i ammunition. While the method of making spherical pellets, comprising quenchngdrops of molten metal,`is the most feasible commercial method of making shot, it is attended by most severe chilling which, inthe manu-V facture of iron sh'ot, consists in a. sudden dropfi'om a temperature above ',2'800?? E. toroom 'temperature pfroA ducing iron pelletsA muchwtoo dhard for` use .in ordinary shot guns. I v '.-'Freatmentofordinaryi-iion: shot by the usual'- annealing techniques does not produce theV characteristicsv` necessaryafor asatisfactory projectiler Heretofore it has been proposed to produce steel ar; tiol'es having a'loword'er ofI hardness from av steel 'casting ori-ngot: byzmechanically working the' metal in a series ofrsteps` followed bytintermediate annealingsteps,l and, prior toithetinal working step, hea-t1 treating in aidecarbu;

rizingratmosphere. Il thenal'workingstepwas of such Yet another disadvantage-ofj l generally stated; tolprodce ,iron y'shot' suitable for us desir'ablelbauistieresults;

' thexautas'thefollowingdescriptionkisireadf" p Intr accordance, withitlierpresent invention, shotgwh" shoe-.these early developments have not.b eeriffollowedlby widespread use of iron shot. "lfliepotentialadvanf tagesr of iron shot have never, been,realizedargelybe- Y,cause iron shot, asy produced, heretofore,havembeem;

' ratus suita-blei forJ carryingiouttlie treatment of fthe r4sin butf helfltw..` the ,A41d transformation point, i so th'atztherre z terior isQimgortant-froin heastandPQin-tsof avoidingndam t, ageiztoa fhechckef character as not to harden thel metalappreciably', no' finali annealingV is necessary: The requirement formechanically working, however, elfiininatesthe possibility-of utilizing4 suchJ a processv upon partsso small as shot? It: has also. been proposed to -treatri'ron- (Iwithor wit-hout'` appreciable.- amount'sf ofv othermetals) sheets, bars,y or

1:400."C; (2"552PF).v but againthese techniques, Whichfessentially include' the:v mechanicall workingj'sfan ante# cedentvto the'heat` treatment; are inapplicableI tshet andf at; the higherftemperatures; the shot will 'deformz Decarburiza'tiorroliunworkedicastings in the same tem? perature` range'- land-*i112J a-l wet hydrogen1 atmosphereil'iasLr` also been proposed (U.S. PatentNo. 2,225,968?, butthe ei'cacyi of` such *treatment has been dependent uponi the andrequired on the orderof'forty hours or more. 'Il "rle presence of the: other metals not only renders-iron sliti unltfor projectileiuse, butthe duration of the ,treatment3 isi son prolonged-that1 its application to shotwouldffcost" more than the shotis worth'.r p

as the projectile inshot1guns;and which will not'abrad or otherwise damage the barrelf-of"tlie shotgun:

Another-object'ofltheinvention is to `rliirvideesttchs f having lphy'f'sial'propertiesfoffa "character 'such as toyie'lv It isualsoanaobjetofthe invention to provide an' app n l ironf'castings;l l v @thero'bjectswwill#becomex apparent :to those skilled is -u'nabrasive-, to f gllnibarrelsfand: which'liasquite satis factory ballistic characteristics; -is pouredv fand'castnfiomt substantially, pureairon-andtthen (without any mechanica i sult'ing ishot .have a hardnessof .'lessgtha'n. 1 l0 V:D.P.H.f,'; and whose hardness Vat ltheir rcentersrf" Y S A v iron, as the expression is used herein, is meant iron which is devoid of deliberate addition of hardening elements, such as chromium, molybdenum, tungsten, nickel, copper, vanadium, etc., and which is as free as practicable from other elements. Such substantially pure iron will usually contain less than a quarter of a percent of impurities, i.e., an iron content of 99.75%.

The hardness values herein stated are all according to the Diamond Pyramid Hardness scale (herein abbreviated D.P.H.). were determined by employing a 13G-degree square base diamond indenter and applying a load of one kilogram on a Tukon tester for 20 seconds, as described in the October 1945 Engineering Achievement Issue of Materials and Methods in the article entitled The Practical Adaptation of the Tukon Tester and the Knoop Indenter, and as described in the February 1949 issue of Modern Machine Shop, in the article entitled Microhardness Testing of Small Tools, by G. E. Shubrooks. On this scale, hard lead, for example, has a hardness value of about 35, zinc and copper have hardness values of from 50 to 60, gun barrels of mild steel have hardness values of from 100 to 130, and chrome molybdenum gun barrels have a hardness of about 240. The hardness values of the iron shot herein referred to were determined after conditioning the shot as follows:

The shot samples were mounted in a methyl methacrylate polymeride plastic, such as Lucite," and the mounting was ground down on an abrasive wheel until approximately one-half the diameter of the mounted shot was removed. The mounting was then polished on abrasive paper having grits 0, 2-0, 3-0, and 4-0. The speciment was then polished on a wheel covered with billiard cloth, while the wheel was kept wet with a liquid abrasive, such as an alumina. After all noticeable scratches were removed, the sample was etched with an acidic solution, such as 2% Nital solution. The specimen was then repolished on a wheel covered with Selvyt cloth using the liquid abrasive. After this final polishing, the sample was etched once more and was then ready for hardness testing.

In order to produce iron shot having physical properties best suited for projectile use, we have found that the micro structure of the finished shot should be coarsegrained and in a single phase. For universal use, i.e., in old fashioned, as well as in modern shot guns, the grain size of the finished shot should be no smaller than ASTM grain size No. 2 (ASTM Standards, 1944, p. 1933) and preferably on the order of Nos. and0, but when the shot are to be used only in guns whose barrels have the hardness of 125 D.P.H. or'higher, grain size as small as ASTM No. 6 may be tolerated. v

We have discovered thatthe desired properties may be imparted to shot as cast from substantially pure iron by heat treatment in a non-oxidizing hydrogen atmosphere above the A3 point, and that desirable properties are developed in such shot without prolonged heat treatment. In practice, the time period above the A3 point may be as short as 30 seconds, but in commercial scale operations five minutes provides a more adequate factor fof safety.

The hardness values herein referred toof impurities other than carbon and nitrogen. We have observed that the nitrogen content of the shot, as cast, has an important bearing on duration and effect of the heat treatment-as with shot containing .M9-.020% nitrogen, as cast, the ultimate shot are somewhat harder and their grain structure smaller than shot containing .GOS-.010% nitrogen as cast.

While the heat treatment can be carried out in an atmosphere of wet hydrogen, it is preferred to maintain the atmosphere as dry (.e., free of water or water vapor) as possible (in contradistinction to the known wet hydrogen annealing techniques wherein enough water is introduced to create an oxidizing atmosphere).` Some water will, inevitably find its way into the heat-treating atmosphere, either as an impurity in the hydrogen supply or as a reaction product from any oxide which may be present on the shot being treated, but so long as the content of water in the treating atmosphere does not exceed about 3%, the atmosphere is considered nonoxidizing and desired results are achieved.

In general, the treatment of iron shot according to this invention involves first providing the as-cast shot (near spheres most of whose diameters are between 0.062 and 0.144 inch) having the following typical analysis:

Iron

If it is desired to produce shot having a hardness consistently well below 100 D.P.H. with a grain size larger than ASTM No. 2, it is important that the nitrogen content of the shot, as cast, not exceed about 0.012%. By melting the metal in a vacuum furnace, and otherwise controlling the conditions so that the nitrogen content is O (or so close to it that it is unmcasurable), a hardness as low as D.P.H. may be achieved with a grain size of ASTM No. 00.

Having provided the substantially pure iron shot with the lowest feasible nitrogen content as cast, the shot are then heated in a hydrogen atmosphere and maintained at a temperature above the A3 point, but below the A4 point, for the time period above-indicated, which may be as short as 30 seconds or longer, depending upon the apparatus employed and other environmental conditions consistent with the rule that the higher the temperature (bclow the A., point) Vand the lower the nitrogen content of the as-cast shot, the shorter the time period of treatment above the A3 point need be.

Having elevated the individual shot to a temperature above the A3 point, while enveloped in the hydrogen, the shot are then quenched in a hydrogen bath and preferably maintained in such hydrogen bath until the tempera- It is essential, however, to avoid heating the shot as high as the A4 transformation point, and therefore the tern` introduced into the heat treatment without 'previous `me chanicalworking, the iron containsv not more than 0.25%

ture of the individual shot descends to 300 F. or less.

The treatment may be carried out either as a batch process or as a continuous process.

, To assure that-the individual shot constituting the charge be uniformly treated, and to minimize the tendency thereof to deform, sinter, or cluster at the temperature of treatment, it is important that the temperature not reach the A4 point, and it is desirable to keep the shot in motion during the heat treatment.

In Vour parent aplication, above-identified, the results given were obtained from batch operations upon shot whose composition was as indicated in the foregoing table. except that the nitrogen content was within the limits of 0.008 to 0.012%; and the shot were maintained at a temperature of 1675 and 1800 F. for periods of 60, 90. 120, and 180 minutes. At the end of the heat treatment. the. shotfwere cooled by the continued introduction of hydrogen until their temperature reached 212 F. or less.

The :results obtained with four separate batches of shot indicated A, B, C, and-D, respectively', were as follows:

The `following table typiiies the chemical analyses the 'shot beforer and after treatment, the results applying specifically to shot from batch AY in the'foregoing table:

Before After Troatm ent, Treatment,

Percent Percent Manganese O. 009 0. 009 Phosphorus- N one N'onc Sulphur; 0. 017, 0.013 Silicon; 0.03 0.030 Nitrogen- 0. 007 0.002 `Carbon 0.050' 0.008

Iron\ Balance Balance Spec'tograp'hicanalysis `of the same sample revealed the nadium, and copper, both before and after treatment." In other samples, vtraces of chromium, tungsten, and cobalt were' found. In any cas`e,'the quantitiesoftrace elements are too minute to measure and do vnot affect the properties of the shot. y y

Subsequent investigations, in which we used a furnace constructed and arranged for the continuous treatment 0f shot, 'have indicatedthat thfe time periodls'kof treatment utilizedin vthe batch operationswere considerablyA longerV than necessary. Utilizing a shaker-hearth type furnacer of the character hereinafter described' more in detail,lwe

begin practically instantaneously, a s eries of shot (batches F,"G and were passed through the furnace "at an accelerated rate (considerably in excess. of the rate at which such shot traveled under the maximum speed ,atr

tainable with the shaker mechanism) so thatthel time lat temperature above 1670* F. was 30, and 300 seconds, respectively. The shot in each batch had average, as cast, D.P.H. values of: Edge 116; center 121, and were all of the same composition, being substantially pure iron with 0.009% carbon and 0.010% nitrogenas cast. The following results were attained:

AFTER ANNEAL D. P. Hardness Content Time above 1670 F., Seconds Batch Center Edge o Carbon,

` Percent I' Percent Range Ave. Range Ave.

In the foregoing examples indicated, batches A to H inclusive, the shot were cast from substantially pure iron` melted in a vacuum furnace so as to minimize the nitro`- gen absorption of the melt. Accordingly, the as cast shot have lower nitrogen content, being on the order of 0.008,-.-

0.010% as indicated, than would be the Ycase when. the

, shot are cast from a melt made in an electric furnace or open hearth. The invention is, however, applicable to, the treatment of shot having higher as ca st nitrogen contents, such as those on the order of 0.0l9'to 0.020%" resulting from an electric furnace melt of substantially pure iron. As illustrating lthe results ofcontinuous hydrof gen-atmosphere h eattreatment theshaker-hearthtype,

' of furnace, with an elapsed time of fourteen ri'iinutefls,V

. 45 presenceof tracesof nickel, molybdenum, aluminum, va-

have lascertained that shot of the same composition and ,Y physical rproperties as that f batches A, B, C,`and,D

above could be treated, in l'a hydrogen atmosphere, in an elapsed timer (from room temperature into the furnace tol room temperature out ofthe furnace) of fourteen minutes where the maximum temperature.attainedbyv shot in the furnace wa s,1850"v F., with thefollowing results: f

D. 12. Hardness"l s Grain 7 Batch Center Surface size Range Ave. Range Ave.V

E f Q 74-80 77.3 V'7445i 76.5 i o0 To establish the fact that the changes in physical properties, as well as the reduction of Ynitrogen and carbon, 75 22007,1 F.

upon shot whose nitrogen contentwas o n the order ofy 0.019 to0.020%, but otherwise of the same composition as that described above (said shotjhaving been cast ,from

a melt made in an electric arc furnace andrjhavinlg an asV cast hardness of 260f350 D.P.H. the following results were attained:

D. 1?,..Hardness j Range Ave. Piangev Ave e i 95. ev 110. 0Y Y 11n the accompanying'drawings, Figure 1 is aldiagrayrn.. matic, view of vthe shaker-hearth type of `furnacevwith`- attachment to which reference lhas `been; made above,"

Figure 2 is a `dia Vnace suitable for usein invention; f.

Figure3 is aphotomicrograph at 100xl magnificationof theg'ranstruCture and individuaL'as cast, shot before treatment; and f f Figure isa photomicrograph atl x magnification of'. the grain structure of an individual shot after treatment. Referring now to Figure 1 of thedrawings for an illusg-y trative embodiment of the shaker-hearth type furnace hereinbefore referred to, then structure may consist/of. concentric tubular shells 1 and 2, between which an electric heating element 3 is disposed. The heating element may bev either an electrical resistance or an induction coi1,j but in either case, must becapablevof elevating the temperatnre of shot pellets within tube 2- to a temperature@- above, 1670 Nitrogen,

ammaticview of` a vertical typefnr- I Vaccordance with the present,v

F., and preferably as high as 1'85f0 F. orf.'

The inner tube 2 is open at one end 4 and is provided with an opening 5 near its opposite end. The tube 2 is preferably formed of refractory material and the exterior tube 1 may likewise be formed of refractory material.

Extending into the tube 2 through the open end 4 thereof is an oscillatible hearth 6, the inner end of which is mounted upon a suitable cradle 7, and the outer end of which is connected to be driven by suitable shaker mechanism 8. The shaker mechanism is of a character such as to move hearth 6 toward opening 5 of the furnace gradually, and then jerk it in the opposite direction, whereby shot deposited toward the outer end of the hearth 6 are moved step by step toward the inner end of the hearth. Above the outer end of the hearth, a feed hopper 9 is provided for depositing the shot to be treated upon the outer end of the hearth 6.

The exterior tube is provided with an opening 11 in radial alignment with opening 5 in the interior tube 2, and a sleeve 12 extends across the space between the openings S and 11, thus providing a conduit. Beneath opening 11, a conduit 13 extends downwardly and constitutes the inner wall of a cooling device 14, whose outer wall 15 is spaced from conduit 13 and provided with a coolant inlet 16 and a coolant outlet 17. The conduit 13 projects beyond the cooling element 14 and is provided with a removable gas-tight closure 18. Between the closure 18 and the cooling element 14, the conduit 13 is provided with a hydrogen inlet 19.

Water, oil, cold air, or any other heat exchange medium may be utilized as the coolant and circulated through the chamber defined between the inner and outer walls 13 and 15 of cooling element 14. In lieu of providing a gas-tight closure at the lower end of conduit 13, the end thereof may be reduced and left open provided the volume of hydrogen gas introduced at 19 is sufficient to prevent the intake of air at the open end of conduit 13. An economy in hydrogen gas is, however, effected by making cooling element 14 of sufficient volume to accommodate the product of a relatively long run of the furnace and then periodically discontinuing the feed of shot to the furnace while the treated shot within cooling element 14 are discharged therefrom by removal of cap 18.

In the operation of the furnace, the shot deposited upon hearth 6 attain a temperature of atleast .1670 P. before they fall from the inner end of the hearth. When the shot fall from the inner end of theY hearth, they are received immediately into the cooling device 7 where, while they are enveloped by hydrogen, they are cooled by giving up their heat to the coolant circulating through the jacket of the cooling device 14, but without contact with oxygen, carbon dioxide, or nitrogen, until their temperature has been reduced to about room temperature, when they may he discharged into the atmosphere. Hydrogen is continuously introduced through opening 19 and travels therefrom through the cooling chamber into the furnace, and through the furnace to opening 4, where it may be burned. l 1

An alternative form of furnace is Yshown in Figure 2 and consists essentially of a vertically arranged induction furnace having an interior induction chamber 21 provided with a spiral ramp 22 to retard the descent of .shot deposited in the top of the furnace. The inclination of the ramp and Vthe height of the furnace .are coordinated with the heating capacity thereof so as to assure that individual shot pellets will be elevated to a temperature of atleast l670 F., and preferably 1850 .to 22007 F.,`as they roll down the spiral ramp 22.V From the bottom of chamber 21, the shot are dropped into conduit"13 leading to a` cooling element of the character hereinabove described. As in the previous embodiment, hydrogen is continuously introduced so as to completely envelop the shot in the any stack effect invchamber 21, which might result in an impoverished hydrogen atmosphere about the shot trav# range of treatment time periods.

eling down the spiral 22, a ceramic core 23 may be provided to fill the space between the inner edges of the spiral ramp. Thus, the hydrogen stream is compelled to follow the spiral path in countercurrent relationship to the downward rolling of the shot.

The apparatus above described provides for the continuous treatment of such shot at any chosen temperature between the A3 and A4 points, and within a considerable As hereinbefore indicated, the essential feature of the invention is the provision of iron shot which will not erode gun barrels, and

while we have herein recited the value of 110 D.P.H. as the maximum hardness which should be tolerated immediately after the heat treatment, it is to be noted that shot, cast from substantially pure iron, age-harden at the rate of about 10% over the first five months, after their treatment according to this invention. Thus a batch of substantially pure iron shot, containing 0.006% carbon and 0.008% nitrogen, before treatment in accordance` with the present invention, had their carbon and nitrogen contents reduced, respectively, to 0.001% and 0.006% during treatment for thirty minutes at 1850 F., and at the end of such treatment, the average edge hardness was 78.1 D.P.H., and the average center hardness, 80.2 D.P.H. After the shot had aged for five months, however, the edge hardness average had increased to 88.0 D.P.H., and the center hardness to 90.0 D.P.H. Thus, by setting a maximum D.P.H. value of 110 for the treated shot, immediately after they are annealed, it is contemplated that theV ultimate hardness, after aging a few months, may reach a value of 120 D.P.H., and such is therefore contemplated by the invention.

A further factor enters into the selection of a critical maximum hardness value, and that is the size of the shot. With No. 9 shot (the smallest size used in commercial shotshells), a hardness as high as 120 D.P.H. is quite suitable yand has no serious deleterious effect upon the barrels of the firearms. At the other extreme, No. 4 shot (which is the largest of the popular commercial sizes used in shotshells) exhibits quite a tendency to erode cornparable gun barrels at a hardness as high as 100 D.P.H. Consequently, for No. 4 shot, it is preferred that the maximum value be 80 D.P.H. (prior to age-hardening) and theother sizes, between Nos. 4 and 9, may have their hardness graduated between the values indicated for Nos.` 9 and 4. Accordingly, the time period of heat treatment between the A3 and A., points is preferably longer with larger shot than with smaller shot, or in the alternative, the temperature of the treatment is higher with the larger shot.

From theV foregoing description, it is believed that those skilled in the art will readily understand the principles of the invention and its mode of operation, and the results accomplished thereby. While a variety of data have been given, showing the flexibility of the process, `it is to be distinctly understood that the invention is not limited to the time periods or temperatures of treatment cited for illustration hereinabove, but that such variations and modifications thereof as may present themselves to those skilled in the art, without departing from the spirit of the invention, are, although not specifically described herein, contemplated by and within the scope of theL appended claims.

Havingithus described the invention, what is claimed and desired to be secured by Letters Patent is:

1 Shot having a diameter between about 0.062 and about 0.144 of an inch and composed of substantially pure unworked iron containing not more than about 0.25% impurities and having a hardness on the order of not more than D.P.H.

2. Shot composed `of substantially pure unworked iron and having grain size larger than ASTM Size 2 and a hardness of not more than about 110 D.P.H.

3. Shot composed of drop cast globules of substantially 9 to 110 D.P.H. and an interior hardness not substantially greater than the surface hardness.

4. Shot composed of drop cast globules of substantially pure unworked iron and having surface hardness of 60 to 1110 D.P.H. and an interior hardness not substantially 5 greater than the surface hardness and not more than about 10 percent in excess of the surface hardness.

Wintherlich et a1 Feb. 24, 1880 Wintherlich et al Dec. 28, 1880 OTHER REFERENCES ASME Handbook on Metal Properties, 1954, pages 3-4. Edited by S. L. Hoyt and published by McGraw- Hill Book Co., New York, N.Y.

Hoyt: Metals and Alloys Data Book, 11943, page 132.

10 Published by Reinhold Publishing Corp., New York, N.Y.

Wilson: Conversion Chart, Chart 52, 1952. Available from Wilson Mechanical Instrument Div. of American Chain and Cable Co., Inc., New York, N.Y. 

1. SHOT HAVING A DIAMETER BETWEEN ABOUT 0.062 AND ABOUT 0.144 OF AN INCH AND COMPOSED OF SUBSTANTIALLY PURE UNWORKED IRON CONTAINING NOT MORE THAN ABOUT 0.25% IMPURITIES AND HAVING A HARDNESS ON THE ORDER OF NOT MORE THAN 110 D.P.H. 